Historically, mobile/cellular networks have been centrally planned to achieve the majority of coverage via long range APs. New-generation networks conforming to the LTE (4G) standards and beyond are being widely deployed alongside 3G (and other legacy) wireless networks. In the present discussion, references to LTE and or wireless networks can include other wireless telecommunications networks as the context permits. All such networks are usually provided in the form of nationally deployed wireless APs known as macrocells, which provide regional coverage over longer range wireless links typically over tens of kilometers. Due to rapid and ongoing growth in demand for data capacities in wireless networks related to the increasing popularity of data-hungry applications on UEs such as laptop computers, smartphones, tablets and such devices (mobile or otherwise), alternatives models are being developed to share the data load. For example, data can be offloaded onto local, short range APs in the form small cell APs in preference to the longer-range macrocell APs. Such small cell APs operate links which transmit (and receive) over distances considerably smaller than macrocells, examples of which include femtocells, picocells, and microcells. In the present discussion, references to “femtocells” include other small cell network types.
These approaches helps relieve the traffic burden on macrocells and can provide a better user experience. Viewed in this way, macrocells are thought to be the primary network and short range APs are a secondary supporting resource. The range of femtocells typically spans distances of tens of meters. In this approach, there would typically comprise one or more femtocell networks within the footprint of a macrocell, and a user moving out of the range of a femtocell AP would expect to “fall back” to a connection with a macrocell AP.
It is known to provide for small cell networks in, e.g., densely populated areas (such as railway stations or concert venues) to meet permanent or temporary spikes in demand on a centrally-planned basis. However, femtocells were originally designed for residential and small business use, so femtocell APs are more commonly used in residential, and small and medium enterprise (SME) premises. They can be configured with the capacity to serve as LTE or LTE-compatible femtocell APs, which collectively between numerous homes and business endpoints can provide the femtocell network coverage and support discussed above by interworking with the macrocell LTE networks. This enables a UE within the wireless network to connect to the femtocell network instead of the macrocell network, allowing for data loads to be shared between the networks. The resulting increased bandwidth and capacity can result in an enhanced quality of service (QoS) and experience (QoE) for customers and users of UEs.
In certain cases, it may be preferred for UEs to connect to the femtocell network over the macrocell network (instead of the more conventional macrocell network providing the primary capacity with femtocells providing secondary, support to mop up spikes in demand). There are certain advantages, both technical and commercial, for such an approach. Where a femtocell network takes on most or even all of the local traffic within its footprint, there is no (or less of a) requirement for macrocell APs to “join up” the local coverage which in certain circumstances may be difficult or costly. The inversion of the usual approach could also reduce the level of connections transferring between macro- and femtocell networks, or repeated connection-flickering (known as “ping-pong”) between the networks. Users would additionally benefit from choosing to remain connected to a particular network for technical or cost reasons, e.g., to avoid roaming charges to a fall-back macrocell network. For network operators or service providers, maintaining a connection on a particular network in preference to another allows improved control over network resources, to maintain consistency of quality standards and also allows for operational efficiencies. Commercial benefits could also be realized by keeping customers on the preferred network and avoiding interconnect charges. At the same time, residential and SME femtocells are by definition limited in power and have to be cost-efficient, so it will be an important part of a solution for these constraints to be taken into account.
In this alternative approach in which the femtocell network serves as the primary network, UEs within a femtocell network would have to be provided with end-to-end connectivity within the defined femtocell network footprint, especially when the users are actively mobile and travelling within the network. A problem arises owing to the potential for patchy connections due to lack of universal coverage within the femtocell network. As noted above, small cell APs were initially intended to provide local coverage or to serve as secondary coverage “infill” or data offload, in support of the primary planned macrocell network. Their ad hoc deployment by residential or SME customers is usually uncontrolled in the sense that a central network operator has no direct control over, or explicit knowledge of, coverage gaps in the femtocell network. For example, an end-user may choose to locate the hub in a part of the premises or in a way which impedes its transmission outside of the premises. A particular hub in the area may suffer an unexpected outage, or be turned off when the end-user goes on holiday. Such femtocell networks are, in this sense, “unplanned” (from the network operator's perspective), and so may not be relied upon to serve as a primary network—or even to support macrocell operations within an LTE wireless network. Such femtocell networks can be contrasted with macrocell networks, which are centrally planned and managed for wide-scale regional or national coverage. For femtocells to more usefully serve a role in the wireless access network, i.e. to take on part of the data load envisaged above, their usability has to be improved so that they can be better structured, located and controlled to provide a predictable and consistent level of coverage for UEs across a defined terrain. It would be desirable to be able to configure a wireless network to realize the above advantages and benefits.
A method in the area of handovers between femtocells and macrocells is described in EP 2485516, in which AP nodes are configured to independently assess the number of connections so that its transmission power can be increased to close coverage gaps. If and when it is determined that a user can be handed over to a neighboring node, the increased transmission power of the particular node is then reined back to drop the connection to that user. In a busy network with much UE movement and handover activity, it may be expected that the transmission power will require constant and continual adjustment, with the attendant risk of accidental connection drops. The described method provides secondary coverage for a network in which a macrocell is the primary data carrier, but does not provide a solution in which the femtocell network is to serve as the main network to which UEs preferentially connect especially when travelling within the area.